Preeclampsia complicates 6-8% of pregnancies (Hauth, J. C. et al., Obstet Gynecol. 95(1):24-8, 2000) with an incidence in the US of 23.6 cases per 1000 deliveries in the US. (Samadi, A. R. et al., Obstet Gynecol. 87(4):557-63, 1996.) In recent statistics preeclampsia was classified as responsible for 20% of pregnancy-related maternal deaths (MacKay, A. P. et al., Paediatr Perinat Epidemiol. 19(3):206-14, 2005.) and the leading reason for a medically indicated preterm delivery (MIPTD) (Fronterhouse, W. et al., J Matern Fetal Med. 10(3):162-5, 2001.) thus responsible for 10% of all premature births. (Fronterhouse, W. et al., J Matern Fetal Med. 10(3): 162-5, 2001.) Preeclampsia (PE) is defined new onset of elevated blood pressure with proteinuria after 20 weeks of gestation. (ACOG Committee on Practice Bulletins. Obstet Gynecol. 99(1):159-67, 2002.) It is considered severe (sPE) if blood pressure and proteinuria are increased substantially or symptoms of end-organ damage including fetal growth restriction occur. The course of severe preeclampsia is associated with a progressive deterioration of maternal condition and iatrogenic delivery remains the only definitive treatment. Management from the part of the caring physician consists of balancing the risks of immediate delivery of an immature fetus against the risks to both mother and child of a complication of preeclampsia. For this, the current approach is close monitoring of maternal and fetal status with delivery remaining the ultimate treatment. (Zamorski, M. A. & Green, L. A. Am Fam Physician 64: 263-70, 216, 2001.) The situation becomes further complicated for the caring physician when there is hypertension or a renal affect pre- or co-existing pregnancy and thus differentiating preeclampsia from similar clinical manifestations becomes very important from a managing standpoint.
From 1 to 5 percent of pregnant women have chronic hypertension (crHTN), defined as sustained hypertension that is present before conception or during the first 20 weeks of gestation. The rates are higher in obese, older, diabetic and black women. Chronic hypertension is a disease process that progresses slowly over years, in contrast to the usually more rapid course of preeclampsia over days. If uncomplicated by preeclampsia crHTN is usually a benign pregnancy complication for mother and child. On the other hand, crHTN predisposes to the risks of preeclampsia and abruptio placentae and thus to increased neonatal mortality and morbidity. The poor neonatal outcome among women with chronic hypertension is usually due to superimposed preeclampsia (spPE), but data regarding risk factors for preeclampsia and for adverse outcomes of pregnancy in women with chronic hypertension are sparse. The diagnosis of spPE is especially difficult in cases of preexisting proteinuria, chronic renal disease or other medical mimics such as systemic lupus flares. (Repke, J. T. J Reprod Med. 43(4):350-4, 1998; Williams, W. W. Jr. et al., N Engl J Med 353: 2590-600, 2005.) Because there is no sensitive or specific test for preeclampsia, the gold standard in such cases is renal biopsy, an invasive diagnostic test which needs to be performed in pregnancy, as a pre-pregnancy real biopsy is generally not predictive of renal outcome in pregnancy and change of histology in repeated biopsies was frequently observed. (Imbasciati, E. et al., Nephron. 36(1):46-51, 1984.)
To this date preeclampsia cannot be treated, except by delivery, and, therefore, efforts concentrate on correct case identification. Thus any preferably non-invasive test that can distinguish candidates for such mandated preterm delivery versus medical management would be helpful to practitioners.